Objective The objective of this study was to find risk factors in pregnancy for post-traumatic stress and depression 1 month after childbirth. Furthermore, the relation between post-traumatic stress and depression was explored.Design A prospective longitudinal study.Setting Pregnant women in Linköping and Kalmar, Sweden.Population A total of 1224 women were assessed in pregnancy, week 12-20 and 32, as well as 1 month postpartum.Methods Post-traumatic stress and depression after delivery were assessed 1 month postpartum. Potential risk factors were assessed in early and late pregnancy. Variables measured during pregnancy were trait anxiety, depression, fear of childbirth, childbirth-related traumatic stress, stress coping capacity, social support, parity, educational level, age, gestation week, parity, educational level, civil status, previous psychological/psychiatric counselling, and previous experience of any traumatic events. Delivery mode was assessed from the medical records.Main outcome measures Prevalence of post-traumatic stress (criteria A, B, C, D, E, and F according to Diagnostic and statistical manual of mental disorders, fourth edition (DSM-IV)) and depression (Beck's depression inventory).Results One month postpartum, 12 (1.3%) women had posttraumatic stress (met symptom criteria B, C, and D for posttraumatic stress disorder according to Diagnostic and statistical manual of mental disorders, 4th edition [DSM-IV]). The most important risk factors in pregnancy were depression in early pregnancy (OR = 16.3), severe fear of childbirth (OR = 6.2), and 'pre'-traumatic stress (in view of the forthcoming delivery) in late pregnancy (OR = 12.5). The prevalence of depression was 5.6%. Post-traumatic stress and depression were positively related 1 month postpartum and were predicted by mainly the same factors.Conclusions Risk factors for post-traumatic stress and depression after childbirth can be assessed in early pregnancy. Post-traumatic stress and depression also seem to share the same underlying vulnerability factors.